Plastic moulding tools are made of a great variety of steel alloys, such as carbon steels, low and medium alloyed steels, martensitic stainless steels, precipitation hardening steels and maraging steels. A summary of existing steel alloys which are employed for the manufacturing of plastic moulding tools can be found in the printed issue of “Tool Steels in the next Century, Proceedings of the 5th international Conference on Tooling, Sep. 29 to Oct. 1, 1999, University of Leoben” (ISBN:3-9501105-0-X) page 635-642. Within the group of martensitic stainless steels there exist a number of commercial plastic moulding steels, including a steel that is manufactured and marketed by the applicant under the registered trade name STAVAX ESR® having the following nominal chemical composition in weight-%: 0.38 C, 0.8 Si, 0.5 Mn, 13.6 Cr, 0.3 V, balance iron and unavoidable impurities from the manufacturing of the steel. That steel is standardized according to SIS2314 and AISI420. Steel of this type has an adequate hardness in the hardened and tempered condition of the steel. The ductility (toughness) and the hardenability, however, do not satisfy the increasingly higher demands which are raised on the materials of today for qualified plastic moulding steels, at least not for tools in large dimensions.